In a communication system, a relay has been introduced to eliminate a shadow area. A repeater technology has been evolved from a simple amplify- and forward method to a method which is made intelligent such as decode-and-forward, reconfiguration/reallocation- and forward, and the like.
In particular, in a next-generation mobile communication system, introduction of a plurality of relays which are made intelligent may be unavoidable in order to enlarge the coverage and to improve data throughput while reducing the costs of installing more base stations and maintenance costs of a backhaul communication network.
In addition, in recent years, a mobile relay whose position is flexible as well as a fixed relay whose position is fixed has been used in a communication system.
However, as to such a mobile relay, there is no problem with data communication when a state of a backhaul link between a donor eNodeB that provides a backhaul link to the mobile relay and the mobile relay is good, but there is a problem with the data communication when the state of the backhaul link is bad.
Therefore, in recent years, there has been a demand for more efficient transmission method of a mobile relay that can transmit and receive data in consideration of the state of the backhaul link.